The research is focused around the use of four different model systems that will be used to assess the potential of the laser for the reduction and/or removal of atheromas from blood vessels. The goals are to examine the mechanisms of laser interaction with atheromas as well as to define the optimal set of laser, fiber optic, and control (imaging) parameters. These studies will assess these parameters in an atherosclerotic rabbit model (acute study); in an in vitro human arterial segment perfusion system where vasoreactivity can be monitored physiologically; in a human atherosclerotic arterial segment that has been grafted into the coronary system of the pig and treated under fluoroscopic guidance; and in an atherosclerotic pig model where the thrombogenicity of the laser treatment sites can be assayed by Indium-111 radiographic imaging. These four model systems will be used to evaluate the laser for both laser endarterectomy and laser angioplasty. These methods will also be combined with histologic analysis. Finally, extensive mutagenesis and carcinogenesis testing will be performed on the ultraviolet laser wavelengths that show promise for non-thermal photoablative removal of plaque.